Various aspects of motion compensation are described in our British Patent Applications Nos. 9020498.3 and 9111348.0 which describe systems capable of generating intermediate fields of video image sequences where the original sequence of images includes motion of, for example, a foreground object moving over a background. Such intermediate fields are required when producing slow motion sequences or for standards conversion.
In many applications of motion compensation an output image is created by cutting and pasting one or more parts of various video images onto a background. The parts of the video images may include motion within themselves and the parts as a whole may be moving over the background.
When such cutting and pasting techniques are used visible discontinuities are often produced in the output image when there is a sharp transition from foreground image to background image. These discontinuities are referred to as `aliases` and the problem of these is well known in picture creation systems. They are removed from pictures by use of `anti-aliasing` techniques which blend the foreground and background pictures together over a few pixels.